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rhel 5 cluster issue

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hi

I wonder how can I manage cluster resources from luci interface such as sap database and sap instance ?

so ı need  know-how to handle failover mechanism

regards

Accepted Solutions (1)

Accepted Solutions (1)

Former Member
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Hi,

your question is quite unspecific, but this document may help you:

https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Linux/5/html-single/Cluster_Admini...

Regards,

Peter

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Hi

especially wondering how  to setup ERS   ınstance  in clustere environment?

sure that ERS should be run on the node where ASCS  is not running

behavıour of sapstartsrv  in boot phase  and     /usr/sap/sapservice icnlude which isntance?

other issues already addressed.

thanks

Former Member
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Hi,

I suppose you mean Enqueue Replication Service?

Yes, the purpose is to keep lock consistency in case of enqueue server failure, therefore it has to be installed on a separate host.

For my understanding you'll have one SCS instance (including enqueue server) on host a, and a ERS installation on host B. ERS will then be started separatedly (not sure about that), and will start another enqueue server if the central instance enqueue fails.

Maybe these links will help you to understand the context:

http://help.sap.com/saphelp_nw04s/helpdata/en/6d/e3a03cc24efd1de10000000a114084/frameset.htm

http://help.sap.com/saphelp_nw04s/helpdata/en/6d/6a853f11ed0617e10000000a114084/frameset.htm

http://help.sap.com/saphelp_nw04s/helpdata/en/de/cf853f11ed0617e10000000a114084/frameset.htm

Regards,

Peter

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Hi

config like that :

1-ASCS instance is as resource in RHEL cluster  (installed   using virtual name)

2-ERS  also resource in RHEL cluster  (also has virtual name same as ASCS  instance)

3-Db instance is also resource in RHEL cluster (installed using virtual name)

3- central instance and additional instance running now with  manually start (startsap R3.....)

4- when I fail node1 all resources passing the other node in cluster.ASCS  instance can follow the  ERS instance.also replication is ok.I check it  with ensmon.

but I came across a problem while failed node is restart.

I saw this process :/usr/sap/.........../exe/sapcontrol -nr 20 -function WaitforStopped 3600 1

when I kill  this process   ,  node is running properly

yu have any idea?

Former Member
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2-ERS  also resource in RHEL cluster  (also has virtual name same as ASCS  instance) --> shouldn't ERS using different virtual name?

Server host name X(x.x.x.1):

ASCS instance -> virtual ip(x.x.x.101)-> virtual host name A

assigned as a resource with virtual host name A

Server host name Y(x.x.x.2):

ERS Instance-> virtual ip (x.x.x.102) -> virtual host name B

assigned as a resource with virtual host name B

scenario:

ASCS Service started in server X with virtual name A

ERS Service started in server Y with virtual name B (replicated shm from server X for ASCS instance).

in event of failure ASCS service is relocated along with its IP resource to server Y so it can start with the shared memory(lock table) replicated by ERS.

for more complete view you can peruse following document ( there is a sample config in its Appendix)

http://www.redhat.com/rhecm/rest-rhecm/jcr/repository/collaboration/jcr:system/jcr:versionStorage/31...

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hi Henry

really I looked that document from rhel   site before.

ı read appendix  A expecially SApinsatance ERS   section.

there is a ERS instance as a resource in cluster.

this instance created how?   it uses a virtual name like ASCS  instance  and DB instance.

really ı wonder  exactly ERS instance  how  should be installed  on 2 nodes  for being resource   in cluster?

Former Member
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older version of sapinst has no option to install ERS so we must deploy it ourself & edit the profile manually. But newer sapinst has an option to install ERS with wizard.

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I know it   but I wonder   ERS instance should be installed using SAPINST   option    SAPINST_USE_HOSTNAME  (virtual hostname)     on 2 node?

thanks 

Former Member
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you can:

1. install it during ASCS Installation( this is what I do most)

2. install it separately (copy all symbolic link in SYS dir - first)

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should I install it every node in cluster using   virtual hostname?  and should that virtual name same  with ASCS  instance's virtual name?

Former Member
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You need to configure ASCS and ERS services with follow_service dependencies

Regards

Roman

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I did it but I want to sure about my ERS instance config.

after failover ASCS follows ERS . it is ok .

ı wonder   , is it correct   ERS setup?  

Former Member
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According to documentation:

"

follow_service(svc1, svc2, master)

Function for a construct when service svc1 and service svc2 should not be running on the same node

even after failover. And if svc1 fails it should follow svc2. Then svc2 is relocated on any other node in the

cluster.

"

I.e. ERS service should be relocated also.

Regards

Roman

Former Member
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If you don't like this configuration try to use SAP polling concept:

"Some HA software solutions do not offer the concept that a software package obeys another package on this package’s host. For this reason SAP has introduced the polling concept: Here, a replication server runs on every possible failover host, and does not have to be controlled by the HA software. Whether you need this or not depends on your HA software. For more information, contact your HA software partner."

Regards

Roman

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according to this statement  :

"follow_service(svc1, svc2, master)"

ERS (so svc2 ) should be installed every node   in cluster? and how can I name  it?

Former Member
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You install ERS service on one node only with it name. After that it is cluster services responsibility to relocate ERS to another node in the cluster with it name (and ip address, and LVM, and fs etc.) according to your cluster configuration. In two-node cluster configuration you install ASCS instance on one node and ERS instance on another and configure follow service dependency between them

Regards

Roman

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thanks Roman

now clear ERS instance

Regards

Answers (0)